The AGTs-BD study is a randomized, open-label, rater-blind, multicenter study, which including an 8-week acute treatment (Phase I), followed by a 24-week recurrence prevention treatment (Phase II), and a 24-week relapse prevention treatment (Phase III). Patients initially enter an up to 4 weeks screening phase to confirm the randomization to whom met DSM-IV criteria of bipolar I or II disorder, currently depressed with Hamilton Depression Rating Scale-17 items (HAM-D) total score ≥17. The protocol was approved by the each sites' appropriate institutional review boards and ethics committees. After screening, patients were randomly allocated to one of three groups: (1) lithium monotherapy; (2) lithium plus quetiapine; (3) lithium plus a Traditional Chinese Medicine (TCM) named as Shuganjieyu capsule (SGJY, St. John's wort and acanthopanax senticosus combination). After phase I, patients who met stable remission, defined as HAM-D total score ≤7 and Young Mania Rating Scale (YMRS) total score ≤10 in two consecutive visit at least 4 weeks, were qualified into phase II and III. Patients remained on the allocated treatment for up to 48 weeks or until treatment failure. The difference between phase II and phase III was that treatment dose could be decreased (within the study ranges) if side-effects became troublesome in phase III, but not for phase II. All patients will be provided with free care (3 visits) by the investigators, for a period of up to 3 months after the end of the study, in order to help them make the transition into routine clinical care.